Flotation process



Patented July 27, 1937 UNITED STATES FLOTA'I'ION PROCESS James EmoryKirby, Wilmington, Del., asslgnor to E. I. du Pont de Nemours & Company,Wilmington, Del., a corporation of Delaware No Drawing. ApplicationFebruary 4, 1936, Serial No. 62,277

Claims.

This invention relates to a method of concentrating ores and saltmixtures by froth flotation. More particularly it relates to theconcentration of ores and salt mixtures containing sodium and potassiumchlorides by froth flotation. Still more particularly it relates to theuse of water-soluble salts of certain aliphatic amines in a frothflotation process for the separation of potassium chloride of highquality from ores and salt mixtures containing that material inadmixture with sodium chloride and other impurities.

A recent development in the domain of ore flotation is that of Lenher asdescribed in his copending patent application, Serial No. 730,551, filedJune 14, 1934. In that application, Lenher describes a number offlotation separations which were diflicult or impossible by previouslyknown methods, and in carrying out these separations, Lenhercontemplates using a class of reagents which has the long-chainsurface-active group in the positive ion. The following are two examplesof flotation reagents belonging to the class discovered by Lenher:

C mHsa Cetyl pyridinium bromide C 17H:5NH3 CI Heptadecylaminehydrochloride The present application deals with the use of certainmembers of this group of new reagents in the flotation of potassiumchloride.

This invention has as an object the development of an improved flotationmethod for the separation of potassium chloride from sodium chloride andother impurities. A further object is the utilization of certain membersof the class of collecting agents having the surface-active group in thepositive ion in a flotation process for the purification of potassiumchloride. Other objects will appear hereinafter.

These objects are accomplished by the use of surface-activereagentschosen from the class of water-soluble salts of normal, primary,aliphatic amines having 6 or more carbon atoms, and preferably 8 to 12carbon atoms in the aliphatic chain, and water-soluble salts ofmono-alkyl substituted guanidines in which the alkyl substituent is anormal, primary, aliphatic radical having 6 or more carbon atoms in aflotation process for the separation of potassium chloride from a pulpcomprising finely ground ore or salt mixture containing potassiumchloride, and a saturated brine prepared from the ore or salt mixture.

The process of this invention may best be understood by reference to thefollowing examples. It is to be understood that the scope of theinvention is in no wise limited to the processes as set forth in theseexamples.

Example 1 A sample of sylvinite ore was obtained from Carlsbad, NewMexico. This ore is composed of about 40% sylvite (potassium chloride),57% halite (sodium chloride) and about 3% of ironstained clay intimatelyassociated with the sylvite. Due to the presence of the clay, thesylvite crystals are pink in color and may be readily distinguished fromthe colorless halite or rock salt crystals. Part of the ore was reducedto minus 40-mesh by means of a Braun disc pulverizer. A saturated brinewas prepared from another portion of the ore by agitating it with waterat room temperature until no more was dissolved. The resulting brine hada specific gravity at room temperature of 1.233. Eight hundred grams ofthe ground ore was then further ground for 30 minutes in a l-gallonpebble mill in the presence of 1 liter of the saturated brine and 3 kg.of flint pebbles. This amount of grinding reduced the ore tosubstantially 100 per cent minus 65-mesh and about 85 per cent minus100-mesh. The slurry of ground ore and brine was then split into eightportions of about 100 g. each by means of an ordinary type of samplesplitter. One of these 100 g. samples was transferred to a smalllaboratory mechanical agitation flotation cell of the type described byJ. F. Gates and L. K. Jacobsen (Engineering and Mining Journal, 119, 19,771 (1925)). The cell was filled to the pulp level by adding saturatedbrine. The agitation was started, and then 2 cc. of a 1% aqueoussolution of n-octyla-mine hydrochloride added. A pink froth carryingsylvite particles quickly formed and was removed from the cell into adry beaker. The froth was sufficiently voluminous that its removal fromthe cell was readily effected without carrying out an excessive amountof the pulp itself. After 4 minutes, the froth had become barren and wasdying out, and at this point, flotation was discontinued. Theconcentrate and tailings were filtered, dried, weighed and analyzed withresults as shown in the following table.

Reagent used: n-octylamine hydrochloride,

0.39 lb. per ton.

Potassium chloride in feed, calcd., 40.98%

Example 2 A second charge of ground ore prepared as in Example 1 wasfloated in the same manner as in the preceding example except thatinstead of the n-octylamine hydrochloride, 2 cc. of a 1% aqueoussolution of n-decylguanidine hydrochloride,

was used as the flotation agent. Again a pink froth, well loaded withsylvite, was produced. After the flotation was complete, the productswere filtered and dried as in Example 1. The concentrate weighed 49.3 g.and consisted of potassium chloride of good quality, while the tailingsweighed 43.4 g. and were practically barren of potassium chloride. Thequantity of reagent used was 0.02 g. or 0.43 pound per ton of feed.

Example 3 The process of Examples 1 and 2 was repeated using 5 cc. of a1% aqueous solution of n-dodecylamine hydrochloride as flotation agent.Flotation proceeded very satisfactorily, a froth loaded with pinksylvite particles being produced. The concentrate, consisting of goodquality potassium chloride, weighed 46.3 g., and the tailings,predominantly sodium chloride, weighed 52.7 g. The amount of reagentused was 1.01 pound per ton of ore.

Example 4 performed to show that the filtrates recovered from aflotation carried out as in Example 1 may be used in subsequentflotations, instead of fresh brine, utilizing the flotation reagentcontained therein to decrease the amount of fresh reagent necessary. Aflotation was carried out as in Example 1 except that 3 cc. of 1%aqueous solution of It-octylamine hydrochloride was added instead of 2cc. as in Example 1. This flotation was termed the first flotation". Theproducts of the first flotation were filtered and dried and thefiltrates preserved. A second charge of ground ore was now washed intothe cell using the filtrates from the first flotation to aid in thetransfer and to fill the cell to the pulp level. One cubic centimeter ofthe n-octylamine hydrochloride sufilced to give a good yield ofpotassium chloride flotation concentrate. This second flotation wascalled the first recirculation". A second recirculation" was carried outlike the first recirculation, using a third charge of ore, filtratesfrom the first recirculation as pulp brine, and 1 cc. of 1% n-octylaminehydrochloride solution. Again, a satisfactory froth and yield ofconcentrate were produced. The results are summarized in the followingtable.

This experiment was The results of Example 4 indicate that in commercialoperation recirculation of concentrate and tailing liquors could bepracticed with a saving in reagent cost and without detriment to theresults obtained.

Example 5 A sample of a crude crystallized mixture of sodium chlorideand potassium chloride was obtained from the Bonneville district ofwestern Utah. This salt mixture had been prepared from a brine obtainedfrom a natural salt deposit. The potassium chloride content of thedeposit as it occurs in the Bonneville district is only a few per cent,the bulk of the deposit consisting of sodium chloride, together withsmall amounts of soluble salts, e. g., magnesium chloride. The brine hadbeen partially evaporated to allow a large amount of sodium chloride tocrystallize out. The mother liquid had then been evaporated further toyield a mixture of salts containing about 24% potassium chloride. Thissalt mixture was used in a flotation test similar to those described inthe preceding examples.

One kilogram of the crude salt mixture was suspended in one liter of abrine saturated with potassium and sodium chlorides and ground in apebble mill until substantially all of the particles were finer than-mesh. The slurry of ground salts and brine was then split into eightportions, and one of these portions subjected to a flotation test in theminiature flotation cell described in Example 1. One cubic centimeter ofa 1% solution of octylamine hydrochloride was added to the charge in theflotation cell, whereupon a well loaded froth quickly formed and carriedover the lip of the cell into a dry beaker. The froth quickly broke inthe receiver, and the floated salt particles quickly settled out.Flotation was complete in 4 minutes. The concentrate and tailings werefiltered out on a Buchner funnel, dried at C. in an oven, weighed andanalyzed for their potassium chloride content. The results of theexperiment are summarized in the following table:

In carrying out the process of purifying potassium chloride asexemplified above, numerous reagents other than the three cited abovewill give satisfactory results. Among them, the following may bementioned:

n-Hexylamine hydrochloride, n-Heptylamine hydrochloride, n-Nonylaminehydrochloride, n-Decylamine hydrochloride, n-Undecylamine hydrochloride,n-Tetradecylamine hydrochloride, n-Hexadecylamine hydrochloride,n-Octadecylamine hydrochloride, n-Octylamine hydrobromide, n-Octylaminenitrate, n-Octylamine acetate, n-Octylguanidine hydrochloride. andn-Dodecylguanidine hydrochloride.

All of these reagents possess a straight chain at least 6 carbon atomsin length in the positive ion of the molecule. It has been found thatthe presence of a straight carbon chain of the specified length isessential to impart collecting power for potassium chloride to theflotation agent. Thus, it has been shown that salts of aliphatic amines,e. g., n-amylamine hydrochloride, tri-n-butylamine hydrochloride, andthe hydrochloride of the branched chain amine, approximately CQHIQNHZ,boiling from ISO-190 C., prepared from a higher alcohol obtained in thecatalytic synthesis of methanol from carbon monoxide and hydrogen willnot produce satisfactory flotation of potassium chloride under theconditions of the above cited examples. Likewise, salts of amines inwhich the amino nitrogen either forms a part of a heterocyclic nucleus,e. g., pyridine hydrochloride, dodecyl pyridinium chloride, and cetylpyridinium bromide, or is attached to an aryl or aralkyl nucleus, e. g.,p-toluidine hydrochloride, alpha-naphthylamine hydrochloride, andbenzylamine hydrochloride will not produce satisfactory flotation ofpotassium chloride under the conditions exemplified herein.

In carrying out the process of this invention, any of the well-knowntypes of froth flotation cells such as the minerals separationsub-aeration type, the Callow cell, the MacIntosh cell, etc., may beused. The ratio of pulp solids to brine may vary from about 1:1 to about1:6. The pulp temperature may vary from about 50 F. to about F. or evenhigher without materially affecting the results. The amount of reagentwill vary somewhat for different ores and different types of watersupply. In some cases it may be as low as 0.05 pound per ton of ore,while in others, it may be as great as 2-3 pounds per ton or evengreater. Usually 0.2-1.0 pound per-ton will suflice. The fineness ofgrinding depends, as in all flotation processes, on the size of theindividual grains present in the material being treated. As in allflotation processes, the various constituents must be "liberated in thegrinding operation. With some ores, grinding to 50-mesh will suflice,while with others it is necessary to grind to ISO-mesh, 200-mesh, oreven finer. The process can be applied only to ores in which thepotassium chloride occurs as such.

One of the uses of this invention is that set forth in Examples 1 to 4;namely, the recovery of potassium chloride of high quality from naturalores containing it. The ability of the flotation reagents to select or"collect the potassium chloride while rejecting the sodium chloride isvery remarkable. Another use of the invention is the recovery ofpotassium chloride from salt mixtures obtained by evaporating todryness, brines obtained from salt wells as illustrated in Example 5.The process is successful with salt mixtures of this kind only when theyhave been crystallized under such conditions that the potassium chloridecan be set free from the sodium chloride, magnesium chloride, and othercontaminants by grinding.

Resort may be had to such modification and variations as fall within thespirit and scope of the appended claims.

I claim:

1. A process for separating potassium chloride from a pulp containingthe same which comprises subjecting said pulp to a froth flotationprocess employing an agent of the class of water-soluble salts ofnormal, primary, aliphatic amines having 6 or more carbon atoms in thealiphatic chain and preferably 8 to 12 carbon atoms in the aliphaticchain, and water-soluble salts of mono-alkyl substituted guanidines inwhich the alkyl substituent is a normal, primary, aliphatic radicalhaving 6 or more carbon atoms.

2. A process for separating potassium chloride from a mixture ofpotassium chloride, sodium chloride, and other impurities whichcomprises subjecting a pulp of said mixture in its'saturated brine to afroth flotation process employing an agent of the class of water-solublesalts of normal, primary, aliphatic amines having 6 or more carbon atomsin the aliphatic chain and preferably 8 to 12 carbon atoms in thealiphatic chain, and water-soluble salts of mono-alkyl substitutedguanidines in which the alkyl substituent is a normal, primary,aliphatic radical having 6 or more carbon atoms.

3. A process for separating potassium chloride from a mixture ofpotassium chloride, sodium chloride, and other impurities whichcomprises subjecting a pulp of said mixture in its saturated brine to afroth flotation process employing an agent of the class of water-solublesalts of normal, primary, alkyl amines having from 6 to 18 carbon atomsin the alkyl group, and water-soluble salts of mono-alkyl substitutedguanidines in which the alkyl substituent is a normal, primary,aliphatic radical having from 6 to 18 carbon atoms.

4. A process for separating potassium chloride from a mixture ofpotassium chloride, sodium chloride, and other impurities whichcomprises subjecting a pulp of said mixture in its saturated brine to afroth flotation treatment wherein a hydrochloride of a normal, primaryaliphatic amine containing at least 8 and not more than 12 carbon atomsin the aliphatic chain is employed as a flotation agent,

5. A process as set forth in claim 4 wherein the mixture being treatedis sylvinite ore.

6. A process as set forth in claim 4 wherein the mixture being treatedis obtained by the evaporating of salt brine.

7. A process as set forth in claim 4 wherein the hydrochloride of analiphatic amine which is employed as a flotation agent is n-octylamiriehydrochloride.

8. A process as set forth in claim 4 wherein the hydrochloride of analiphatic amine which is employed as a flotation agent is'n-dodecylamine hydrochloride.

9. A process for separating potassium chloride from a mixture ofpotassium chloride, sodium chloride, and other impurities whichcomprises subjecting a wulp of said mixture in its saturated brine to afroth flotation treatment wherein a hydrochloride of a mono-alkylguanidine in which the alkyl substituent is a normal, primary, aliphaticradical having at least 8 and not more than 12 carbon atoms in thealiphatic chain is employed as a flotation agent.

10. A process as set forth in claim 9 wherein the hydrochloride of amono-aikyl guanidine which is employed as a flotation agent isn-decylguanidine hydrochloride.

' JAMES EMORY KIRBY.

